JPH0283252A - Normal-pressure production of combined sintered material of zirconium oxycarbide and aluminum oxide - Google Patents

Abstract

PURPOSE:To obtain a combined sintered material of Zr oxycarbide and Al2O3 sintered at high temperature under normal pressure by embedding compressed powder of a mixture of ZrC powder having particle diameters in a specific range and Al2O3 powder in Al2O3 powder and sintering. CONSTITUTION:A mixture of (A) 15-50wt.% ZrC powder (particle diameter: 3-10mum) and (B) 85-50wt.% Al2O3 powder is compression molded to give compressed powder, which is embedded in Al2O3 powder. The embedded material is sintered normal pressure at 1,700-1,900 deg.C to give a high-density (93-97% relative density) combined sintered material of zirconium oxycarbide [ZrCxOy (0<x<1, 0<y<1, 0.5<=x+y<=1, 0.05<=y/x<=0.22)] and Al2O3. Addition of <=5wt.% based on Al2O3 of MgO or Y2O3 raises density of sintered material and improves oxidation resistance. The sintered material is useful as cutting tool material, wear-resistant material, heating element material useful in an oxidizing atmosphere and electroconductive material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a composite sintered body of zirconium oxycarbide and aluminum oxide.

This composite sintered body is useful as a material for cutting tools, a wear-resistant material, a heating element material that can be used in an oxidizing atmosphere, and an electrically conductive material.

Conventional technology Ah02 has excellent properties such as high strength and high hardness, but has the drawback of low toughness. Therefore, high hardness,
By combining ZrC with high strength and high toughness, ZrC-^1.0. has excellent mechanical properties. It is known to use composite ceramics.

Further, although ZrC has excellent electrical conductivity, it has a drawback of poor oxidation resistance. Therefore, it has excellent oxidation resistance^1 to
Z that combines the advantages of both by combining with ff
It is also known to use rCAItO:+ conductive ceramics.

However, all of these composite ceramic sintered bodies are manufactured by a hot pressing method that applies high loads at low temperatures. That is, since ZrC, one of the components, is difficult to sinter, a load is required for sintering, and at high temperatures A1. Since the evaporation of O, becomes significant, it has been manufactured by the above method.

As described above, the conventional method requires a high load, which makes the manufacturing equipment expensive, complicates the manufacturing process, increases the manufacturing cost, and makes it impossible to produce a sintered body with a complicated shape.

Moreover, the obtained sintered body has ZrC-A I□0. Only a two-phase system could be obtained.

Furthermore, as for the pressureless sintering method, it is a well-known fact that when a green compact is embedded in AltO3 powder and fired, the sintered density increases. (Proceedings of the 1986 annual meeting of the Ceramics Association, presented by the present inventors, p. 455) This controls the sintering atmosphere and prevents the evaporation of aluminum oxide from the green compact to prevent compositional changes. , in order to increase densification.

However, since optimization of the particle size of ZrC had not been considered, the upper limit was a relative density of about 90%.

Purpose of the Invention The present invention was made in order to eliminate the drawbacks of the conventional method.The purpose of the present invention is to use zirconium carbide and aluminum oxide as raw materials, and to have a higher density than the conventional method (relative density 93-97%). It is an object of the present invention to provide a method for producing a composite sintered body having excellent properties, which is made of zirconium oxycarbide whose sides are substituted with oxygen and aluminum oxide.

Structure of the Invention In order to achieve the above-mentioned object, the present invention has a particle size in a specific range (3 to 3).
A green compact is made by specifically blending zirconium carbide powder with a diameter of 10 μm) and aluminum oxide powder, or a compact is made by adding a small amount of magnesium oxide or yttrium oxide powder, and this green compact is wrapped in aluminum oxide powder. Bury it in a neutral or reducing atmosphere for 1
It has been found that when pressureless sintered at 700 to 1900"C, a composite sintered body with high density and excellent properties that could not be obtained by conventional methods can be obtained despite the pressureless sintering. It was found that the sintered body is a composite sintered body containing zirconium oxycarbide and aluminum oxide.The present invention was completed based on these findings.

The gist of the present invention is that 15 to 50% by weight of zirconium carbide powder with a particle size of 3 to 10 μm and 85 to 5% of aluminum oxide powder
A homogeneous mixture containing 0% by weight of magnesium oxide or yttrium oxide powder, or a homogeneous mixture in which magnesium oxide or yttrium oxide powder is added in an amount of 5% by weight or less based on aluminum oxide, is formed into a compact, and this compact is embedded in aluminum oxide powder. The present invention provides a method for producing a composite sintered body of zirconium oxycarbide and aluminum oxide, which is characterized by sintering at 1700 to 1900'C under normal pressure in a neutral or reducing atmosphere.

The blending ratio of zirconium carbide powder and aluminum oxide powder in the present invention is in the range of 15 to 50% by weight of zirconium carbide and 85 to 50% by weight of aluminum oxide. If the content of zirconium carbide is less than 15% by weight, the toughness, electrical conductivity, and hardness of the obtained sintered body will be low, and if it exceeds 50% by weight, it will not be highly dense and the oxidation resistance will be poor.

The particle size of the raw material zirconium carbide is 3 to 10
It is necessary to use μm.

If the particle size is smaller than 3 μm, the amount of aluminum oxide evaporated during firing will be large, making it difficult to obtain a highly dense sintered body, and if the particle size is smaller than I
If it exceeds Oμ, the progress of sintering will be inhibited. Therefore, it is necessary to prevent the zirconium carbide powder from being crushed to a particle size of less than 3 μm during mixing of the raw material powder. When mixing in a ball mill, it is preferable to use a pole such as a nylon pole.

The purpose of adding magnesium oxide or yttrium oxide powder is to increase the density of the sintered body. The addition also improves oxidation resistance. However, if the amount added exceeds 5% by weight, the sintered density will decrease.

If the pressureless sintering temperature is lower than 1700° C., the amount of evaporation of AlxOi will be small, but the driving force of the substance required for sintering will not be sufficient, and sintering will not proceed. When the temperature exceeds 1900°C, the compacted powder becomes A1□0. Even if it is embedded in powder, the amount of evaporation of AhO* will increase, which will not only change the composition, but also make it impossible to obtain a dense sintered body.Therefore, it is necessary to sinter within the range of 1700 to 1900°C. It is. The atmosphere needs to be neutral or reducing in order to prevent oxidation of the ZrC during sintering.

The sintered body obtained by the method of the present invention is a zirconium oxycarbide ZrC, IQ, in which the carbon sites of zirconium carbide are substituted with oxygen, (Q < x < 1, o <
y<i, 0.5≦x+y≦1.0.05≦y8≦0
．． 22) and aluminum oxide.

In ZrCll0y, x+y is dominated by the non-stoichiometry of ZrC as a raw material. Further, the ratio y/x of carbon to oxygen becomes smaller when the sintering temperature is lower, and becomes larger when the sintering temperature is higher. In the present invention, when the sintering temperature is 1700''C, y/x=0.
05. At 1900°C, y/x=0.22. Therefore, in the method of the present invention, 0.05≦y/x≦0.2
2 things are obtained.

Using a starting material with a composition of 35% by weight of ZrC and 65% by weight of Alz (h), the particle size of ZrC was changed, and MgO or Y,
0. Figure 1 shows the relationship between the sintering temperature and the relative density of the obtained sintered body in the case of adding (0.5% by weight of ^1tos).

In the figure, MU indicates that the ZrC particle size is 3μ or less, * indicates that the ZrC particle size is 3 to 10μ, ◯ indicates that qgo is added, and the stamp indicates that YtOs is added.

As shown in the figure, ZrC with a grain size of 3 to 10 μm has a higher sintered density, and when MgO or Y2O is added, the relative density increases. When the sintering temperature exceeds 1900°C, the sintered density does not increase, and the temperature is 120. evaporation increases.

1850 by varying the starting material composition and ZrC particle size.
Figure 2 shows the relationship with relative density in the case of pressureless sintering with 'C.

In the figure, M indicates that the particle size of zirconium carbide is less than 3 μm, ・ indicates that the particle size of zirconium carbide is 3 to 10 μm, 10 indicates MgO,
As shown in the figure, which shows the case where YzOs (0.5% by weight of AI!Oa) is added, zirconium carbide is
5% by weight is required, and if it exceeds 50% by weight, a highly dense sintered body cannot be obtained.

Figure 3 is a diagram showing the relationship between the relative density and the case where the amounts of MgO and VtOs added to a starting material having a composition of 35% by weight of ZrC and 0.65% by weight of At were sintered at 1850°C under normal pressure. . In the figure, ・ means no additives, as shown in the figure, −
The effect of MgO addition is slightly larger for go, y, and o. Further, the addition amount is effective up to 5% by weight, and if it exceeds this, the relative density will decrease.

FIG. 4 shows the room temperature conductivity of the sintered body when 0.5% by weight of MgO is added to AhOs and ZrCx0. A diagram showing the relationship between the amount of It can be seen that the sintered body produced by the method of the present invention has excellent electrical conductivity.

Example 1゜ZrC powder with a particle size of 3 to 10 μm and A1.03 powder with an average particle size of 0.5 μm were weighed so that the composition ratio of ZrC was 35% by weight, ethanol was added to this, and a nylon ball was added. The mixture was mixed for 12 hours using a . After drying this mixed powder, it was made into a pellet-shaped molded body by -shaft molding and isostatic pressing.

This compact was embedded in AIJs powder in a SiC crucible, and heated and sintered at 1700 to 1900° C. in a high frequency furnace in an Ar flow.

The weight loss of the sample during sintering was less than 1%, and the relative density of the sintered body was as high as 94-96%.

On the other hand, using an alumina ball, ZrC powder was
When a sintered body was made in the same manner using a sample having a diameter of ~3 μm, the weight loss of the sample during firing was 2 to 3%, and the relative density of the sintered body decreased to 91 to 92%.

Example 2゜ ZrC powder with a particle size of 3 to IO μm and Altos powder with an average particle size of 0.5 μm were used, and the composition ratio of ZrC was 15.3.
Weigh it so that it is 5.50% by weight, and further add A1□03
0.5% by weight of MgO powder (average particle size 0.2μ
m) or Y2O powder (average particle size 0.5 μm) was added to prepare a mixed powder, ethanol was added thereto, and the mixture was mixed using a nylon ball for 12 hours. After drying this mixed powder, it was made into a pellet-like molded body by -axial processing molding and isostatic pressing.

This compact was embedded in Altos powder in an SLC crucible and heated to 1,700 to 1
It was heated and sintered at 900°C. As a result, a dense sintered body with a relative density of 95% or more was obtained.

A chemical analysis was performed on the obtained sintered body, and it was found that ZrC is zirconium oxycarbide in which oxygen is solidly dissolved (ZrCx
Oy ) was found to have changed.

Raw material composition of ZrC35 weight%, It0365 weight%,
and 00.5% by weight of Mg were mixed and fired at 1700° C. and 21900° C. The composition of the sintered body was as shown in Table 1 below.

Example 3 ZrC powder with a particle size of 3 to 10μ and an average particle size of 0.5μ
7) Using Al2O, powder, mixed powder with ZrC of 35.50% by weight, and MgO powder (Al2O, off powder)
Example 2
A powder compact was made in the same manner. This is ^ItOs
It was embedded in N powder and heated to 1850°C in an Ar flow.

Composition, relative density, Pinkers hardness, toughness, and 3
The point bending strength was as shown in Table 2.

Table Composition of starting raw material Firing temperature ZrC 35% by weight 1700°C + Altos 65 composition of sintered body Zrf': o, qs Oo, os 35.1% by weight
+ A1□os 64. Heel weight % 1900'C ZrCe, at 06. +s 35. Road weight% 10 AIzOs 64.7 weight% ZrC34, heel weight% + AhOs 64.7 weight% + Mg00.5 weight% 1700℃ ZrCo, 950o, as 34.9 weight% + A1□o! 64. Weight% + MgOO, s 9% 1900℃ ZrCo, 820o, re 35.0% by weight + ^hos 64.5% by weight + MgOO, 5% by weight As shown, it has high hardness, high toughness, and high strength. , suitable as cutting tools, wear-resistant members, structural materials, etc.

Furthermore, Y! 0. The oxidation resistance was examined by leaving the sintered body in the air at 1500'C for 5 hours and measuring the weight change. The results were as shown in Table 3.

Table-3 ZrCo, 12oO, If 34.8% by weight ^1t (h 64.2% by weight + YzOs 1.0% by weight 93.5 4.7 ZrCo, 5soo, +, 34.2% by weight 94.0 4.5 + AI, O! 62.9% by weight + Yz (h 2.9% by weight As this result shows, the weight change is also small.

Effects of the Invention The present invention uses ZrC powder and ^1803 powder as raw materials, in particular, uses ZrC powder with a particle size within a specific range, and embeds this green compact in aluminum oxide powder and sinters it to produce a Pressure sintering has the effect of producing a composite sintered body of ZrCx0y and AhOs with a higher density than conventional ones, which has excellent properties that could not be obtained by conventional methods.

[Brief explanation of the drawing]

Figure 1 shows that the raw material composition is ZrC35 in the method of the present invention.
ZrC using raw materials of 65 wt%
Figure 2 shows the relationship between the sintering temperature and the relative density of the obtained sintered body when the particle size of ZrC is changed and MgO or Y2O is added. Relationship diagram with density, Figure 3 is MgO or Y2O
, and the relative density of the obtained sintered body. The relationship diagram is shown. Fig. 1 Fig. 2 Temperature &'c Raw material Fuji z (zrc +F) fitZ ') Fig. M2O, Y203 outward 0f AI203 += 4 + 3 r amount 2 Fig. To the preparation of the multi-meter length relief tongue body;

Claims (1)

[Claims] 1) Zirconium carbide powder with a particle size of 3 to 10 μm 15 to 5
A mixture of 0% by weight and 85 to 50% by weight of aluminum oxide powder was formed into a green compact, the green compact was embedded in aluminum oxide powder, and the mixture was heated to 1700% by weight in a neutral or reducing atmosphere.
A method for producing a composite sintered body of zirconium oxycarbide and aluminum oxide, which comprises sintering at a temperature of ~1900°C under normal pressure. 2) A mixture of 15 to 50% by weight of zirconium carbide with a particle size of 3 to 10 μm and 85 to 50% by weight of aluminum oxide powder is mixed with magnesium oxide or yttrium oxide in an amount of 5% by weight or less based on the aluminum oxide, and then compressed. The compacted powder is embedded in aluminum oxide powder and heated at 1700 to 1900°C in a neutral or reducing atmosphere.
A method for producing a composite sintered body of zirconium oxycarbide and aluminum oxide, which comprises sintering at normal pressure.